Twist drill



June 5, 1951 CQGSDILL 2,555,302

TWIST DRILL Filed Aug. 25, 1947 INVENTOR.

GLEN H. COGSDILL WW, X?

ATTORNEYS Patented June 5, 1951 'rwis'r DRIL Glen H. Cogsdill, Plymouth, Mich assignor of one-half to Floyd F. Gogsdili, Detroit, Mich,

Application Augus 25, 1947, Serial NQ- 7 .3 9

1 Claim. (Cl. 7 7.fi 8) The present invention relates to a twist drill and more particularly to a lubricated, helically fluted twist drill.

It is an object of the present invention to provide a twist drill having a lgngitudinally extending oil passage throughout its major portion and a plurality of inclined straight oil passages at its tip portion communicating at their innerends with the first mentioned oil passage.

It is a further object of the present invention to teach a novel method of providing a lubricated twist drill which is characterized by the steps of forming a separate shank and tip, providing interfitting torque transmitting formations between said shank and tip and providing separate straight drilled oil passages in the shank and tip which are adapted to be in cemmunication when t han a i ti a e ass mbled o her.

oth r q i c and ea res of he ntion will become apparent as the description proceeds, especially when considered in conjunction with the accompanying drawings, wherein:

Figure 1 is a side elevation of the operating end of an assembled twist drill constructed in accordance with the present invention;

Figure 2 is a side elevation of a portion of the shank part of the twist drill;

Figure 3 is a side elevation of the tip part of the twist drill;

Figure 4 is a top plan view of the tip part illustrated in Figure 3;

Figure 5 is a bottom plan elevation of the tip part illustrated in Figure 3; and

Figure 6 is a bottom plan view of the shank part illustrated in Figure 2.

It is desirable in twist drills of the type referred to, to provide a supply of oil at the bottom of the hole being drilled. In accordance with the present invention, oil passages are formed which open into the end of the twist drill so as to provide oil at the bottom of the hole being drilled.

The twist drill illustrated at In in Figure l is composed of two elements, a shank or body portion shown in Figures 2 and 6 and a tip portion 40 shown in Figures 3 to 5. Referring first to the shank or body portion 20, this portion is provided with a plurality of helically extending flutes 2| leaving intermediate ribs or blades 22 as is conventional in the art. 20 is provided with a transverse groove 23 which as illustrated in Figure 2 may be of rectangular cross section and. which is of a dimension to leave adequate supporting material at its sides. Extending longitudinally through the lower port on At one end the shank 2 of he s ank Z s an 1 ass g 2 w ch is preferably coaxial with the shank portion. The Oil pa a 24 at i s pe end y open on wardly through the end of the drill or it may open laterally thereof. The only essential requirement is that it be arrangedso as to afford connection with a source of oil under pressure.

Referring now to Figures 3 to 5, the tip of the twist drill'is formed as a separate element. It is provided with helically extending flutes 4| which are adapted to provide a continuation of the flutes 2|, the flutes 41 forming intermediate ri so b a e 41 T e end ofh twist r l s tapered to provide the end surfaces 43 and 44. The inner end of the tip is cut away to leave t ngue 4.5 of c oss sect on a a t t fit snugly within the groove, 23. The central portion of the tongue 45 is cut away to provide a slot indicatedat 6 hich term teral y enlarged oil chamber, as will subsequently appear.

In order to provide for a flow of oil at the end of the cutter tip, straight inclined oil passages 41 and 48 are provided. The oil passages 41 and 48 are arranged to extend substantially along the ribs 42.

The assembled twist drill is shown in Figure l and it will be observed that the tongue 45 is inserted within the groove 23. This results in the formation of a laterally enlarged oil chamber l2 which is formed by the transverse slot previously described. The elongated axial oil passage 24 formed in the shank 20 communicates With the top of the chamber [2 and the straight inclined oil passages 41 and 48 communicate with the bottom of the chamber [2.

In producing the twist drill, the shank 20 is provided with a slot by a suitable operation, such for example as milling or broaching. In a similar manner, the tip 40 is provided with the transversely extending tongue 45 by a milling or broaching operation. After the tongue 45 has been formed the transverse slot 46 is produced by a suitable operation, such for example as milling, broaching or the like. The dimensions of the transverse slot 46 are such as to provide an oil chamber 12 of a size adapted to communicate with the oil passages 24, 41 and 48 and at the same time to leave sufficient material therein to transmit torque between the shank and the tip and to provide a strong tool.

The oil passage 24 may be drilled in the shank of the tool and in like manner the straight inclined oil passages 41 and 48 may be drilled in the tip thereof. After the interfitting tongue and groove construction has been provided and the several oil passages drilled, the shank and the tip may be hardened by conventional heat treatment and thereafter the parts assembled together and brazed or otherwise secured in assembled position. As a final operation the twist drill may be finish ground as is usual in tools of this type.

The present construction renders the manufacture of the lubricated twist drill a relatively simple matter and at the same time permits the production of a lubricated twist drill in sizes smaller than has heretofore been considered practicable. At the same time, the provision of the oil holes and oil chamber is such as not to substantially weaken the completed twist drill, and the particular type of connection between the shank and tip of the twist drill is found well adapted to contribute to the'ultimate strength of the completed too], since the tongue and groove connection is well suited to transmit torque between the parts and the portion of the tongue which has been cut away to provide the laterally enlarged oil passage is that portion of the tongue which would contribute least to torque transmission.

The drawings and the foregoing specification constitute a description of the improved twist drill in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claim.

What I claim as my invention is:

A twist drill having a pair of helical flutes and corresponding helical ribs, said drill comprising a relatively long shank portion and a relatively short tip portion, the adjacent ends of said portions having a tongue and groove torque transmitting connection, the tongue and groove being located in ribs at the ends of said portions, the

central portion of said tongue having a trans- I verse slot therethrough defining a laterally enlarged oil chamber when said tongue and groove are interfitted, an axially extending oil passage in said shank portion communicating with said chamber, straight inclined oil passages in said tip portion opening at one end into the end face of the drill and at the other end into said chamber, said last mentioned passage being inclined in conformity with the helix angle of the drill and each disposed generally within a rib thereof the length of said tip being sufliciently short so that each of the straight passages extending from the end surfaces thereof into said chamber lies wholly within a helical rib.

GLEN H. COGSDILL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 496,253 Federschmidt Apr. 25, 1893 589,576 Rickey Sept. 7, 1897 1,048,035 Campbell Dec. 24, 1912 1,104,989 Hanson July 28, 1914 1,285,869 Wineman Nov. 26, 1918 1,407,328 Glenzer Feb. 21, 1922 1,409,753 Moore Mar. 14, 1922 2,148,805 Cogsdill Feb. 28, 1939 2,237,901 Chun Apr. 8, 1941 2,259,611 Burger Oct. 21, 1941 2,325,973 Nurnberger et a1. Aug. 3, 1943 2,360,385 Anderson Oct. 17, 1944 FOREIGN PATENTS Number Country Date 15,608 Great Britain July 27, 1916 21,155 Great Britain May 22, 1913 

